RICK regulates the odontogenic differentiation of dental pulp stem cells through activation of TNF-α via the ERK and not through NF-κB signaling pathway

miR-153-3p inhibited osteogenic differentiation of human DPSCs through CBFβ signaling

Dental pulp stem cells (DPSCs) have multilineage differentiation potential and especially show a great foreground in bone regeneration engineering. The mechanism of osteogenic differentiation of DPSCs needs to be explored exactly. As a kind of endogenous and non-coding small RNAs, microRNAs (miRNAs) play an important role in many biological processes including osteogenic differentiation. However, the mechanism of miR-153-3p in osteogenic differentiation of DPSCs is still unknown. Core-binding factors-beta (CBFβ) is a non-DNA-binding factor that combines with the runt-related transcription factor family transcription factors to mediate their DNA-binding affinities, and plays a critical role in regulating osteogenic differentiation. In this study, we explored the mechanisms of miR-153-3p and CBFβ in DPSC osteogenesis. The expression of miR-153-3p and CBFβ was tested under the osteogenic condition, and the influence led by changing the expression of miR-153-3p or CBFβ had also been detected. A luciferase reporter assay confirmed that miR-153-3p directly targeted to CBFβ. The osteogenic markers, alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and bone morphogenetic protein 2 (BMP2), were tested in protein level or mRNA level. ALP and Alizarin red staining were used to detect the osteoblast activity and mineral deposition. In osteogenic condition, the expressions of CBFβ and osteogenic markers were upregulated, whereas that of miR-153-3p was downregulated. miR-153-3p negatively regulated the osteogenic differentiation, and overexpression of CBFβ could offset the negative effect of miR-153-3p. Our findings provided a novel strategy for DPSC application in treatment of bone deficiencies and facilitated bone regeneration.

NOD2 is involved in regulating odontogenic differentiation of DPSCs suppressed by MDP through NF-κB/p65 signaling

Dental pulp stem cells (DPSCs) are well known for their capable of both self-renewal and multilineage differentiation. Dental tissue diseases, include caries, are often accompanied by inflammatory microenvironment, and muramyl dipeptide (MDP) is involved in the inflammatory stimuli to influence the differentiation of DPSCs. Nucleotide-binding oligomerization domain 2 (NOD2), a member of the cytosolic Nod-like receptor (NLR) family, plays a key role in inflammatory homeostasis regulation, but the role of NOD2 in DPSCs differentiation under inflammatory is still unclear. In this study, we identified that MDP suppressed odontogenic differentiation of DPSCs via NOD2/ NF-κB/p65 signaling pathway. Alizarin red staining and ALP activity showed the odontogenic differentiation was suppressed by MDP in a concentration-dependent manner, and the expression of dentin differentiation marker protein dentin matrix protein 1 (DMP-1) and dentin Sialophosphoprotein (DSPP) also indicated the same results. The expression of NOD2 increased gradually with the concentration of MDP as well as the phosphorylation and nuclear translocation of p65, which meant NF-κB signaling pathway was activated. Further, the interference of NOD2 inhibited the phosphorylation and nuclear translocation of p65 and reversed the MDP-mediated decrease of odontoblast differentiation of DPSCs. Our study showed that MDP can inhibit the odontoblast differentiation of DPSCs in a concentration-dependent manner. The NF-κB signaling pathway was activated by increasing expression of NOD2. Interference of NOD2 reversed the negative ability odontoblast differentiation of DPSCs in the inflammatory environment. Our study might provide a theoretical basis for the clinical treatment for dentinogenesis of DPSCs.

Extracellular IL-37 promotes osteogenic and odontogenic differentiation of human dental pulp stem cells via autophagy

The osteogenic and odontogenic differentiation of dental pulp stem cells (DPSCs) contribute to restoration and regeneration of dental tissue. Previous study indicated that interleukin-37 (IL-37) was an anti-inflammatory factor that affected other pro-inflammatory signals. The aim of this study was to explore the effects of IL-37 on the differentiation of DPSCs. DPSCs were cultured in growth medium with different concentrations of IL-37. We selected the optimal concentration for the following experiments by alkaline phosphatase (ALP) activity analysis, quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blot. Cell counting kit assay (CCK-8) and 5-Ethynyl-2'-Deoxyuridine (EdU) assay were conducted to assess the effects of IL-37 on the proliferation of DPSCs. ALP activity assay and staining, alizarin red S (ARS) staining, qRT-PCR, Western blot as well as immunofluorescence staining were conducted to assess differentiation ability of DPSCs. Western blot, immunofluorescence staining and transmission electron microscopy (TEM) were utilized to examine cell autophagy. Results showed that IL-37 enhanced the osteogenic and odontogenic differentiation ability of DPSCs with no significant influence on the proliferation of DPSCs. Autophagy in DPSCs was activated by IL-37. Activation of autophagy enhanced osteogenesis and odontogenesis of DPSCs, whereas inhibition of autophagy suppressed DPSCs osteogenic and odontogenic differentiation. In conclusion, IL-37 increased osteogenic and odontogenic differentiation via autophagy.